1. Field of the Invention
The present invention relates to a capacitive touch sensing device and, more particularly, to a capacitive touch sensing device by detecting induced electric field.
2. Description of Related Art
Currently, in the research and development of a capacitive touch sensing device, the major affecting factor of self-capacitance lies in the electric field from a human body which is affected by the electric field from the earth. Since an electric field has a positive one and a negative one, it will create differences in increasing or decreasing of capacitance with respect to the self-capacitance, resulting in instability in measuring and being mistaken as noise to deal with.
On the other hand, the size and distance of a contact point on a capacitive touch sensing device will affect the increasing of the self-capacitance and will also affect the magnitude of an induced electric field. In the prior art, it utilizes the feature of capacitance increment to measure if there is a contact, while the ratio of capacitance increment is essentially dominated by the electric circuit design, with a variation approximately 1-2%. However, such variation is far smaller than that of the electric field. Therefore, if the electric field from a human body and the electric field from the earth are treated as noises, it will tremendously affect the accuracy and stability of the capacitive touch sensing device.
Therefore, it is desirable to provide an improved capacitive touch sensing device by detecting induced electric field to mitigate and/or obviate the aforementioned problems.